This invention relates to a rotor of a rotating machine which is an electric generator or an electric motor. More specifically, the invention relates to a motor of a rotating machine, comprising a body portion having a rotating shaft mounted therein substantially integrally, and being composed of a nonmagnetic material; and permanent magnets and magnetic members provided integrally with the body portion and arranged radially and circumferentially alternately in intimate contact with each other.
An example of a rotor constituting a rotating machine which is an electric generator or an electric motor includes a rotating shaft, a sleeve fitted to and mounted on the rotating shaft, permanent magnets and magnetic members arranged radially on an outer peripheral portion of the sleeve circumferentially alternately in close contact with each other, and a pair of side covers disposed on axially opposite side surfaces of the sleeve, each of the permanent magnets and each of the magnetic members, and holding the sleeve, permanent magnets and magnetic members while sandwiching the sleeve, permanent magnets and magnetic members in an axial direction. The sleeve and the pair of side covers are each formed of a nonmagnetic material such as austenitic stainless steel or an aluminum alloy. Each of the magnetic members is composed of a laminate of metal plates comprising a magnetic material, for example, electromagnetic steel sheets.
The sleeve is keyed to the rotating shaft, and thereby coupled thereto integrally. On an outer peripheral surface of the sleeve, there are formed grooves spaced in a circumferential direction and extending in an axial direction. At a radially inward position, corresponding to each of the grooves, in each of the magnetic members comprising the laminate of electromagnetic steel sheets, there is formed a protrusion extending radially inwardly. Each of the magnetic members is disposed such that the magnetic members cannot rotate relative to the sleeve coupled to the rotating shaft, because the protrusion of the magnetic member is fitted into the corresponding groove formed in the outer peripheral surface of the sleeve. Each of the magnetic members has a projection extending radially outwardly of each of the permanent magnets. In each of the projections, a flange portion extending circumferentially bilaterally outwardly is formed. In this condition, consider a state in which each of the magnetic members is disposed on the sleeve, and each of the permanent magnets is inserted into, and held in, a radial space formed in the circumferential direction of each of the magnetic members. In this state, a radially outward end of each of the permanent magnets is held by each of the flange portions opposed with spacing in the circumferential direction so that the permanent magnets will not escape radially outwardly. Between the pair of side covers, a plurality of through bolts are disposed in such a manner as to pass through one of the side covers, each of the magnetic members, and the other side cover. An end portion of each of the through bolts is clamped by a nut. As a result, each of the permanent magnets and magnetic members arranged on the outer peripheral portion of the sleeve coupled to the rotating shaft has the axially opposite side surfaces thereof squeezed between the pair of side covers, together with the sleeve, whereby the permanent magnets, magnetic members, and sleeve are connected together integrally with the rotating shaft. A radially outward end surface of each of the magnetic members is an arcuate surface of substantially the same shape. These radially outward end surfaces are positioned with spacing in the circumferential direction on a circular outer peripheral surface having the same axis center as the rotating shaft (i.e., the spacing formed between the adjacent flange portions opposed in the circumferential direction).
In the conventional rotor constituted as above, a stronger magnetic field for upgraded performance of a rotating machine has been obtained by applying means which make the radial length of each of the radially arranged permanent magnets as large as possible and also make the magnets multipolar. However, the following problems arise when the radial length of each of the permanent magnets is made as large as possible, and the number of the permanent magnets is maximally increased for multipolar function: The circumferential width of each of the magnetic members arranged so as to circumferentially alternate with each of the permanent magnets is excessively small. Moreover, the distance from the outer peripheral surface of each of the magnetic members to the radially inward end of each of the permanent magnets becomes large. Thus, magnetization after assembly becomes quite difficult. In recent years, the performance of permanent magnets has markedly improved, and small permanent magnets can provide a strong magnetic field. Hence, a strong magnetizing force is applied when imparting magnetism. If the circumferential width of each of the magnetic members is excessively small, saturation of the magnetic flux occurs during the magnetizing action after assembly, making it impossible to impart magnetism to each of the permanent magnets as desired. In addition, if the distance from the outer peripheral surface of each of the magnetic members to the radially inward end of each of the permanent magnets is large, it becomes more difficult for a magnetic flux to enter a portion nearer to the radially inward end of each of the permanent magnets. This makes it even more difficult to impart magnetism. The outcome is that despite the increased number of the permanent magnets for a multipolar function, the performance of the rotating machine, which is an electric generator or an electric motor, cannot be improved to a desired degree.
Furthermore, the foregoing conventional rotor is composed of many kinds of and a large number of components, such as the rotating shaft, the sleeve, the keys for coupling the rotating shaft and the sleeve, the plurality of permanent magnets, the plurality of magnetic members, the pair of side covers, and the plurality of through bolts and nuts. Besides, these varieties of many components have to be gathered and assembled. Consequently, the number of the components is large, and many man-hours are required for assembly. The assembly work is laborious, and the burden on labor is heavy. A relatively long assembly time is required, boosting the manufacturing cost as a whole.
An object of the present invention is to provide a novel rotor for a rotating machine, in which the number of permanent magnets is increased to form multipoles, and even after their integration, each of the permanent magnets can be magnetized fully reliably to improve performance.
Another object of the invention is to provide a novel rotor for a rotating machine, in which the number of permanent magnets is increased to form multipoles, and even after their integration, each of the permanent magnets can be magnetized fully reliably to improve performance; whose structure is simple and whose components are small in number; and which can be manufactured at a lower cost than in earlier technologies.
Still another object of the invention is to provide a novel rotor for a rotating machine, in which escape of each of permanent magnets can be prevented reliably, and even after the permanent magnets are integrated, each of them can be magnetized fully reliably to improve performance.
According to the invention, there is provided a rotor for a rotating machine, comprising a body portion having shaft means mounted therein substantially integrally, and being formed of a nonmagnetic material; and permanent magnets and magnetic members provided integrally with the body portion, and arranged radially and circumferentially alternately in intimate contact with each other; wherein the circumferential length between radially outward ends of circumferentially opposite side surfaces, of each of the magnetic members, in intimate contact with the adjacent permanent magnets, is set to be larger than the radial length of each of the permanent magnets.
Preferably, the circumferential length between the radially outward ends of the circumferentially opposite side surfaces of each of the magnetic members, in intimate contact with the adjacent permanent magnets, is set to be 1.5 to 2.0 times the radial length of each of the permanent magnets.
Preferably, the body portion has a substantially circular outer peripheral surface and opposite side surfaces, each of the permanent magnets being completely embedded in the body portion, and each of the magnetic members having only a radially outward end surface thereof exposed and having other surfaces thereof embedded in the body portion.
Preferably, each of the magnetic members has a projection extending radially outwardly of each of the permanent magnets, a space portion being formed in the circumferential direction by the adjacent projections outwardly of a radially outward end surface of each of the permanent magnets, the body portion being disposed so as to fill the space portions and a gap among radially inward side surfaces of each of the permanent magnets and each of the magnetic members, as well as an outer peripheral surface of the shaft means, and so as to cover axially opposite side surfaces of each of the permanent magnets and each of the magnetic members to a predetermined thickness, and the exposed radially outward end surface of each of the magnetic members being substantially coplanar with the outer peripheral surface of the body portion.
Preferably, on one or both of the circumferentially side surfaces of each of the permanent magnets in a radially outward portion thereof, a radially outward inclined surface extending linearly in a direction in which the opposite side surfaces approach each other toward a radially outward end thereof is formed until the outward end.
Preferably, on one or both of the circumferentially side surfaces of each of the permanent magnets in a radially inward portion thereof except the radially outward portion thereof, a radially inward inclined surface extending linearly in a direction in which the opposite side surfaces approach each other toward a radially inward end thereof is formed until the inward end, and the radially inward inclined surface is formed on the circumferentially side surface on the same side as the circumferentially side surface where the radially outward inclined surface has been formed.
Preferably, the length of the radially inward inclined surface in each of the permanent magnets is formed to be greater than the length of the radially outward inclined surface.
Preferably, the circumferential width of the radially inward portion except the radially outward portion in each of the permanent magnets is formed to be constant in an entire region of the radially inward portion.